This invention relates to surgery and more particularly to percutaneous or endoscopic transection of the transverse carpal ligament.
First described in 1933, carpal tunnel release surgery is now considered the most frequently performed operation in the United States. Although carpal tunnel syndrome can be caused by a variety of clinical disorders (hypothyroidism, diabetes, pregnancy etc.), occupational injury or repetitive strain syndrome is now the most frequent association. Indeed, carpal tunnel syndrome is second only to back injuries as the most common reason for employee absenteeism. With repetitive use of the hand, the transverse carpal ligament is thought to hypertrophy thereby compressing the median nerve running beneath it causing the compression neuropathy known as carpal tunnel syndrome.
The carpal tunnel is formed dorsally by the proximal row of carpal bones. Ventrally, the broad ligament known as the transverse carpal ligament extends from the hook of the hamate bone medially to the trapezium bone laterally to form the roof or ventral boundary of the carpal tunnel. Within the tunnel pass the flexor tendons of the hand, the median nerve and associated synovial tissues associated with the flexor tendons.
While a variety of temporizing measures can be used to treat the condition (splinting, anti-inflammatory medication, steroid injection), only surgery is considered curative. Because surgery for this condition enjoys a very high success rate with low morbidity, it is frequently chosen as the definitive treatment option.
The surgical treatment of this condition can be broadly divided into two types: open versus minimally invasive (endoscopic or percutaneous).
With the open procedure, the skin lying over the carpal tunnel is incised and the transverse carpal ligament is then transected under direct vision. The skin is then reapproximated with sutures.
In the endoscopic version, small portals are made in the skin and the transverse carpal ligament is transected endoscopically or through small portals without major disruption of the overlying skin and subcutaneous tissues. In the percutaneous method the ligament is incised using small skin portals similar to the endoscopic method but does not need the use of an expensive endoscope to achieve the same result. Because the majority of pain receptors are located in the skin, limiting surgical trauma to the ligament results in significantly less pain attributable to the procedure and a shorter convalescent period.
Since endoscopic or percutaneous procedures involve smaller skin incisions as compared to the open procedures, they are favored by many surgeons in the treatment of this condition. Present endoscopic procedures require passing an endoscope and associated cutting instruments through the carpal tunnel to facilitate the endoscopic operation. In severe forms of carpal tunnel syndrome, the hypertrophied transverse carpal ligament renders the carpal tunnel quite narrow. Indeed, this is the pathologic process by which the median nerve becomes compressed. When the carpal tunnel is narrow, it becomes difficult and sometimes impossible to pass all of the necessary equipment needed to perform the release surgery. This occurs because the endoscope and associated instruments have a fixed diameter which the pathologically narrow carpal tunnel may not be able to accommodate. For this reason, fully 15% to 20% of endoscopic procedures cannot be completed and must be converted to open procedures. In addition, even in successful endoscopic procedures, significant parathesia may be noted postoperatively because of damage to the median nerve that occurs when surgical endoscopes and instruments are passed through a pathologically narrow carpal tunnel.
Therefore, one object of this invention is to avoid the need for an endoscope in performing percutaneous carpal transverse ligament transection.